The technology described herein relates to graphics processing systems and in particular to methods of and apparatus for determining the position on a volume intersected by a vector when rendering images for display.
When rendering images, such as output frames, for display in graphics processing systems, it can often be necessary to determine the position on a volume intersected by a vector. For example, in environment mapping (e.g. reflection mapping) techniques, the position on a bounding volume intersected by a (e.g. reflected) vector is determined. The intersection position is then used to determine a sampling vector to be used to sample a graphics texture that represents the surface of the bounding volume.
In these techniques, the bounding volume is used to approximate the environment (e.g. room) of the scene being rendered. Typically, a relatively simple bounding volume, such as a bounding box (a cube) or a bounding sphere, is used so that the intersection point can be analytically determined in real-time (at run time) in a relatively simple and efficient manner.
While these techniques can be effective where the environment of the scene being rendered corresponds closely to the, e.g. cubic or spherical, bounding volume being used (e.g. to a box or sphere), it can often be the case that the bounding volume does not match exactly to the surface of the scene being defined. This can cause noticeable errors in the rendered image, e.g. in the reflections, generated using the environment mapping technique.
The Applicants believe therefore that there remains scope for improved graphics processing techniques where the position on a volume intersected by a vector is determined.
Like reference numerals are used for like components where appropriate in the drawings.